Display panel

ABSTRACT

A display panel consisting of a plurality of lines of display modules with each line having the capability of providing a plurality of characters which are produced by electrical signals through a magnetic transducer at a write position and removed by reset magnet with each line of display modules moving upwardly on an endless belt after completion of writing in a line and wherein the vertical movement of the belt is indexed in synchronism with the movement of the magnetic transducers between the write and non-write position.

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PATENEDm 2a m4 saw luw 12 SKU `0S N12 PATNTEDm 2a m4 snm uw 12 FIG.

DISPLAY PANEL BACKGROUND OF THE INVENTION Panels of various types are available for converting electrical signals to visual displays. Many of these panels are designed for special applications while others are provided for a variety of uses. The panel design in a particular application depends upon a variety of factors. The form in which the signal cornes to the panel determines frequently the manner in which the panel will function in response thereto. The speed of receipt of signals is a factor in determining the speed of response in the panel and where it is a moving display system, such as where the characters are displayed and then removed` the time of display must be related to the purpose of the display. For example, where the display and characters are in terms of words, they must be present a sufficient length of time for the viewer to be able to determine the words being displayed. The panel, then, is a combination of electrical, electromagnetic and mechanical structures and these must be synchronized among each other in order to achieve a high speed visual display panel.

SUMMARY OF THE INVENTION A high speed visual display panel in which a plurality of display modules are arranged side by side in a moving blanket to provide each line of which a selected number are visible at one time. Each line is capable of producing a plurality of characters. The blanket is indexed so that the lines move upwardly and means are provided to produce the characters in a line from electrical signals. The character producing means is synchronized with the upwardly moving blanket so that a minimum portion of each cycle is required for placing characters on display.

DESCRIPTION OF THE DRAWINGS FIG. l is a perspective view of a display panel constructed in accordance with the teachings of this invention in which there are visible six horizontal lines and 48 vertical rows so that each of said lines has a 48 character capability;

FIGS. 2A and 2B provide a vertical, longitudinal, sectional view taken along the line 2A,B-2A,B in FIG. l in the` direction of the arrows illustrating four identical write head subassemblics horizontally aligned, each of which provides the capability of'one-fourth of 48 characters in each line and with the module blanket removed;

FIG. 3 is an exploded view of one of the write head subassemblies shown in FIG. 2A, B;

FIG. 4 is a transverse, vertical, sectional view taken along the line 4-4 in the direction of the arrows in FIG. 2B illustrating the drive sprocket and driving guide systems for the display blanket comprising I7v rows of modules with magnetic flags which form the visual portion of the display panel;

FIG. 5 is a vertical` sectional, partially diagrammatic view of a module;

FIG. 5A is a diagrammatic face view of a module with the character "A" displayed;

FIG. 6A is a partially sectional view of a module taken along the line 6--6 in the direction of the arrows in FIG. 5 with the pins thereof received within slots in a write head;

FIG. 6B is a segmentary view taken along the line 6B-6B in the direction of the arrows in FIG. 5 showing flags in display positions;

FIGS. 7, 8 and 9 are enlarged transverse, vertical, partially sectional views taken along the line 7, 8, 9-7, 8, 9 in the direction of the arrows in FIG. 4 illustrating the mechanism for coordinating the movement of the write heads and module blanket with each of these views illustrating a different step in the sequence;

FIG. 10 is a partially sectional end view of the display panel taken in the direction of the arrows lll-l0 in FIG. 2B illustrating the retractA pawl mechanism and 1 blanket drive; and

FIGS. ll and l2 are enlarged fragmentary views similar to FIG. 10 illustrating different steps in the sequence. Y

DESCRIPTION OF THE PREFERRED EMBODIMENT The display panel which is the subject of this invention is shown in perspective in FIG. l and indicated therein by the numeral 20. It consists of l7 lines, each line being composed of a plurality of display modules arranged side by side. Six lines are visible at one time and in the Figs. these lines are indicated by the numerals 2l, 22, 23, 24, 25 and 26 respectively. Each of the lines contains 48 display modules thereby giving each line a 48 character capability. The display modules are arranged one above the other providing 48 rows, the last five of which are indicated by the numerals 27, 28, 29, 30 and 3l respectively in FIG. l. The modules are arranged on an endless belt system so that the characters are first written and displayed in the lowermost visible line, such as line 2l, which is then moved upwardly to take the position of line 22 after all ofthe characters to be displayed in line 21 have been displayed. In FIG. l the numeral 32 designates the lower fluorescent lamp assembly which projects its light upon the modules in the display panel.

As will appear below, each of the display modules is provided with character-forming means which are presented in a read or non-read position depending upon the character to be formed by that module. At one point in the vertical movement of the lines, the character to be displayed in a particular module is developed and that character remains intact as the line moves upwardly until it is erased.

The display panel shown in the Figs. utilizes four identical write head subassemblies horizontally aligned, each of which provides the capability of one-fourth of 48 characters in each line. These are shown in FIGS. 2A, 2B where the blanket is removed and the write head subassemblies are indicated by the numerals 33, 34, 35 and 36. A transverse sectional view is taken along the line 4 4 in the direction of the arrows in FIG. 2B and shown in FIG. 4 illustrating the display modules arranged to form the endless blanket. In FIG. 4 the modules which provide row 27 of FIG. l are shown. For simplicity, each module will be identified by the numeral 37 in this description of the preferred embodiment and each write head by the numeral 38. Module 37 is in position whereat characters are being formed therein and this is referred to as the current writing position. Modules 37a contain information on display and are in display position. Modules 37b contain information but are not visible to the viewer. Modules 37C have been placed in condition where no character is formed, that is, the viewing surface of each has been cleared. As will be explained below, the modules as a blanket are driven by drive sprocket 48. FIG. 3 is an exploded view in perspective of one of the write head subassembiies shown in FIG. 2A, B. lt is noted that the blanket rotates around the write head subassembly and that the modules shown in FIG. 3 are not considered part of the write head assembly. The lines of modules vare linked by blanket rods which` also are not considered part of the subassembly. In FIG. 4 these rods are labeled respectively by the numerals 49, 50, 51, 52, 53, 54, 5S, 56, 57, 58, 59, 60, 6l, 62, 63, 64 and 65.

Each module 37 has an upper hook member 37u formed thereon at its inner upper edge as shown in FIG. 5 for attachment to a blanket rod such as the rod 49 shown in FIG. 4. Likewise, each of the modules has two lower hooks 371 spaced for engagement with a blanket rod beneath it such as blanket rod 65 shown in FIG. 4. The lower hooks are spaced so that the upper hook of the module beneath it can fit between the lower hooks. The hooks are formed so that they can snap on to respective blanket rods.

Each module 37 provides one character which is formed by 35 pivotally mounted circular lightreflective. character-forming flag members. The character-forming members are arranged in seven rows horizontally aligned and five columns. The module is formed with seven horizontal slots 39 in FIG. 5 and the character-forming members are pivotally mounted rearwardly thereof. ln FIG. 5 the character-forming flag members which project through the slots to form visible characters are indicated by the numeral 40 and those that are in position so that they do not project through the slots to contribute to the formation of the character by their visibility` are indicated by the numeral 4I. Seven pins are visible in FIG. 5 projecting rearwardly from the module and these pins are indicated by the numeral 42. A magnet 40' or 41 is mounted on each flag 40 or 4l respectively. In FIG. 5A the character A has been formed. The orientation of the polarity ofthe magnetization of pins 42 determines whether the associated flag member will be positioned for view or not. Hence in FIG. 5 the pins 42 associated with character-forming members 40 are magnetized for display while the pins 42 associated with the characterforming members 41 are magnetized for non-display. ln FIG. 6B the character-forming members 40 are shown projecting through the slot 39. In FIG. 6A thewrite head 38 is shown containing coils 45, only five of which are shown but 35 of which are utilized. The write head 38 is mounted onthe printed circuit card 44 which receives signals from a character generator not part of this invention. Each solenoids 45 when in the write position, receives therein a pin 42 of its respective module 37. There are seven rows of pins 42 associated with each module arranged in five columns to provide 35 pins 42. Likewise, there are seven coils 45 arranged in five columns in each write head. This provides the means whereby the character-forming members can be positioned to be visual or non-visual so that each module has the capability of forming one character. When the module is in the write position, the solenoids in column A in FIG. 5A are activated sequentially (for minimum capacity power supply usage) and current in selected solenoids reverse the magnetization of the respective memory pin 42 rotating the flag into view. In

FIG. 5A to form the character A the pins have been actuated as follows: In column A the pins A-2 thru A-7 are first actuated sequentially, then B-I, B-4, C-I, C-4, D-l, D-4 and E-Z thru E-7. It should be noted as will appear below, each memory pin is of square-loop" material and always magnetized one state for write one state for non-write and each write head is activated in sequence.

As mentioned above, the display panel is provided with a plurality of modules arranged as a blanket with six lines visible at one time, each of the lines containing 48 display modules. The display modules are arranged as an endless belt so that the characters are first written and displayed in the lowermost visible line which is then moved upwardly to take the position of the line above it. The system has mechanism for moving the blanket of modules and also for moving the respective write heads into position where the solenoids 45 of the write heads can be moved into position surrounding respective pins 42.

Turning now to FIGS. 7, 8 and 9, a printed circuit board 44, upon which write head 38 is mounted, is shown. The board is mounted on write head carrier 74 by means of four posts 77, two of which are visible in FIGS. 7, 8 and 9. Each ofthe posts 77 is firmly fastened to the write head carrier 74, however, the printed circuit card 44 is attached to the posts loosely in that there are holes 78 through which pins 79 of the posts 77 project with the holes 78 being slightly larger than the pin 79. Pin 79 has a suitably enlarged head thereon, however, so that the board 44 will not become disengaged from post 77. Pins 80 project from the posts 77 with spring 8l between the pin 8U and board 44 providing a loose fit enabling easy receipt within the solenoid of the pins 42. The write head carrier 74 is mounted on a bracket 82 which has wheels 83 received in track 84 formed on the end plate 66. The write head carrier 74, therefore. is capable of movement toward and away from the module 37. The write head carrier 74 is attached to write head carrier shaft 85 by linking members 86 and 87. Linking member 86 is pivotally attached to the write head carrier at 88 while an end of link 87 is rigidly attached to the write head carrier shaft at 89. Links 86 and 87 are pivotally connected to each other at 90. Hence, oscillation of write head carrier shaft 85 results in to-and-fro movement of the write head 38.

In addition to the movement of the write head carrier via write head carrier shaft 85, the pawl shaft 76 is provided to control the movement of pawl 75 between a position where it can receive a blanket rod, such as that shown in FIGS. 7 and 8, to a position where it is free ofa blanket rod, such as the position shown in FIG. 9. Surface 75a of the pawl is shaped to hold rod 43 in position while the write head is being inserted in the module. This prevents the rod from bowing out and breaking memory pins in the solenoid. The pawl is T-shaped and one end of its arm is pivotaliy connected at 91 to link 92 which is fastened to the pawl shaft 76. A bracket 93 projects downwardly from the I-beam spacer 70 and a spring 94 is attached thereto. Brackets 93 and spring member 94 are right-angled with the surface 93A of bracket 93 providing a track for rolling movement thereon of wheel 95 attached to the end of pawl 75. Additionally, a wheel 96 is attached to the end of spring member 94 to allow for rolling movement of the pawl thereon with the pawl body between wheels 95 and 96, thus confining the pawl body to move in a predetermined path. Oscillatory movement, therefore, of shaft 76 results in controlled movement of pawl 75 between the position shown in FIG. 7 where it can receive a blanket rod and the position shown in FIG. 9 where it cannot interfere with the movement of a blanket rod.

In FIG. 7 the pawl is projecting for receipt of the blanket rod 43' as the module blanket moves upwardly. At this time the write head assmbly is in position rearwardly of the device so that there is clearance between the pins 42 of the modules 37 and the write head. In FIG. 8 the blanket is halted with the pawl 75 embracing the blanket rod 43' and the write heads is forward position with the respective pins 42 of module 37 received within the respective solenoids 45. This is referred to as the write position. The utilization of the pawl mechanism enables the modules 37 to be precisely positioned in order to prevent interference with the movement of the write heads 38 into the write position. The solenoids have been energized selectively in the position shown in FIG. 8 so that the character-forming flag members of module 37 in the write position provide the character desired if a character is to be placed on that particular module. Magnet 112 shown in FIG. 4 is used to place the flags in non-display position. The field direction of magnet 112 is such that as the memory pins enter its field, they are fully saturated by the magnet in order to place the pins on a known position of the hysterisis curve. Continued movement through the field brings respective pins into positions where reversal takes place. This provides a reliable system since there is a fixed, predetermined point for beginning each magnetization cycle.

The movement of pawls, write heads and blankets are accomplished and synchronized by a series of motors, cams, switches and linking systems. There are two motors used in the device; drive motor 97 and stepping motor 98.

Operation is started by actuation of the stepping motor 98 in any one of three ways; a line feed signal, a carriage return signal or after a character has been formed in the last position. A cam 99 is mounted on the shaft of the motor 98. Cam 99 is rotated from the "home" position of FIG. 8 into the retract" position of FIG. 9 where the retract microswitch 100 is actuated to activate the line feed motor and deactivates the stepping motor. In the retract position the write heads are in the rearmost position and the solenoids are cleared from the display module memory pins.

In order to go from home position of FIG. 8 to retract position of FIG. 9, arm 109 is moved rearwardly with the counterclockwise rotation of cam 99. Links 104, 105 and breaker arm 150 which are pivoted about common point 151 are operated when arm 109 strikes roller 152 of the breaker arm 150. The breaker arm breaks links 105, 106 and spring member 153 (see FIG. 12) completes rotation of rod 76 through arm 107.

As seen in FIGS. ll and l2, when points 151, 154 and 155 are in alignment, all of the force of rotation on rod 76 and clamping block 107 is through a straight line and, therefore, the system is perfectly aligned. When force "F" is applied from rod 43 the center of movement is about shaft 76 and force "T" is against the solid biickstop member 93. Adjustable stops 159 and 160 are shown in FIG. 1I and are adjustable to ensure that pivot points 151, 154 and 155 are in alignment.

Actuation of microswitch 100 stops the operation of the stepping motor and turns ori drive motor 97 which rotates the module blanket by means of sprocket 48 and cam 156 begins through the linking system the movement of pawls 75 forward. Cam follower 101A is positioned to ride upon the surface of cam 156 and through links 101, 102 (which are rigidly connected), 103, 104, 105, 106 and 107 rotate pawl 75 into the fully extended and locked into position condition of FIG. 8 wherein the blanket rod 43 can be received thereby. This motion is sensed by module rods 43". end cap 157 and sensor 158 which stops the drive motor and actuates the stepping motor. Upon actuation of the stepping motor, the linkages 109, 108 rotate the write head shaft 85 inserting the write heads through the action of the stepping motor. As this occurs, the write heads are moved to have the solenoids encompass the memory pins 42 of the write head modules. The cam continues to rotate until switch 110 is actuated by cam 99 completing the sequence.

An important feature of the invention is that at approximately three-fourths through the cycle the rod stop pawl is in the stop position shown in FIG. 7. The position of module rod 43 is sensed and speed of the line feed motor is reduced for a gentle stop. In order to accomplish this, means are provided for sensing the end of rod 43". FIG. 11 also illustrates the three-quarter point in the system. An end cap 157 is mounted on rod 43" which engages sensor switch V158 at the three-quarter movement point. The repositioning of the rod stop pawl 75 is through the use of cam 156.

The module rod 43' is stopped by pawl 75. When the home position is reached, the line motor is stopped and this is the position shown in FIG. 8. The write head solenoids have bell mouths 159 which allow for selfalignment on the memory pins. The bell mouth configuration is the first in the alignment process. There is friction between the wide head screws '79 which mount the write heads on board 44 and nylon washers 160. Also, there is friction between nylon washers 161and the board 44 under pressure of spring 81. There is a predicted amount of force due to the presence of the springs. This is a mechanical memory system. If the modules are out of alignment beyond this memory system, rods 77, which are flex rods, flex. Additionally, the outside of head 38 is silicon rubber to absorb shock.

The system utilizes a unique reflector system for uniform illumination of a large area. This is illustrated in FIG. 1 where metalized mylar tape 162 and 163 reflects light from bulbs 164 and 165 respectively rearwardly where it is again reflected by reflectors 166 and 167 respectively onto the modules in the viewing position.

l claim:

1. A display panel including in combination, a plurality of display modules each of which is capable of forming and visually displaying a character, a plurality of lines of display modules provided by the arrangement of groups of said display modules in side by side relationship within each line, a plurality of rows of display modules provided bythe modules in said lines disposed one above the other as an endless blanket, a module write position in which characters are formed in modules of one of said lines disposed therein, a read position in which lines of modules having characters formed therein are displayed to view, indexing means for moving said blanket to sequentially present a different line to said module write position and respectively remove a line from the read position while presenting a new line to the read position, a write head assembly supported within said panel, a write head writing position, write head moving means for shifting said write head assembly in and out of said write head writing po sition, transducer means of said write head assembly for receiving and converting character forming signals to visual characters in said modules when said modules are in said module write position and said write head assembly is in write head writing position, pawl means, a blanket stop engaging position of said pawl means, pawl moving means for moving said pawl means into and out of said blanket stop engaging position, and control means for synchronizing said indexing means and said pawl moving means and said write head moving means to present one of said lines in said module write position, said pawl means in said blanket stop engaging position and said write head assembly in said write head writing position such that the write head has moved into position after the pawl means has stopped the blanket.

2. A display panel in accordance with claim l in which each module contains upper and lower hook members formed thereon and a blanket rod is provided between each of said lines with which said hooks engage to form said endless blanket.

3. A display panel in accordance with claim 2 in which said pawl means includes a plurality'of pawls each of which has a blanket rod engaging surface which engages said blanket rod in said blanket engaging position and which is shaped to encompass a portion of the surface of said blanket rod preventing bowing thereof.

4. A display panel in accordance with claim 2 in which sensing means are provided to sense the presence of a blanket rod in a predetermined position thereof to affect said indexing means to reduce the speed of movement ofsaid blanket as said module write position is approached by one of said lines.

5. A display panel in accordance with claim l in which said pawl means includes a T shaped pawl with one arm thereof formed to embrace said blanket in said blanket engaging position, a pawl shaft, link means attaching the remaining arm of said pawl to said pawl shaft, a track surface formed on said display panel, wheel means on the body of said pawl riding on said track surface and said pawl moving means rocking said pawl shaft for movement of said pawl in and out of said blanket engaging position.

6. A display panel in accordance with claim S in which said pawl moving means includes first and secondlink arms, a first pivotal attachment connecting said link arms, a second pivotal attachment of the remaining end of said first arm and said link means, a breaker arm, a third pivotal attachment connecting the remaining end of said second link arm and said breaker arm, said breaker arm being movable by said control means whereby upon alignment of said first, second and third pivotal attachments said pawl is locked in blanket engaging position.

7. A display panel in accordance with claim l in which each module contains a plurality of pivotally mounted` light reflective. character forming flag members and a display magnet mounted on each flag meniber whereby the influence of a magnetic field determines the position of each of said flag members and pins of each of said modules formed of a square loop magnetizable material projecting rearwardly of said respective module in operative association with respective display magnets and said transducer means includes magnetizing means cooperable with each of said non-display magnets sequentially to determine the position of said respective flag members by affecting the magnetization of said pins, and a non-display magnet supported within said panel with its magnetic field diposed so that lines pass therethrough prior to entering the module write position, with the field direction of the non-display magnet such that each of said pins as it enters its field is saturated and placed on a known position of the hysterisis curve and continued movement through the field brings respective pins into positions where reversal takes place providing a predetermined magnetization condition of each pin prior to its entry into the module write position.

8. A display panel in accordance with claim l in which said write head assembly includes a write head carrier supporting said transducer means and said transducer means consists of a printed circuit board, posts supporting said printed circuit board on said write head carrier in spaced relation thereto and a write head mounted on said printed circuit board, and in which holes are provided in said printed circuit board through which enlarged head pins project for engagement in said posts, said holes being slightly larger than said pins, friction washers disposed upon said circuit board on either side of said hole, and spring means are provided yieldingly urging said printed circuit board away from said posts and in contact with the heads of said pins providing a friction memory mount.

9. A display panel in accordance with claim 8 in which said posts are flex rods.

10. A display panel in accordance with claim l in which said write head assembly includes a write head carrier supporting said transducer means and said transducer means consists of a printed circuit board, posts supporting said printed circuit board on said write head carrier in spaced relation thereto and a write head mounted on said printed circuit board, and in which each of said modules includes a plurality of rearwardly projecting pins and each of said write heads includes a plurality of solenoids each of which is received to receive a respective pin as the core thereof with the entrance to said solenoid being in the form of a bell mouth.

1l. A display panel in accordance with claim 10 in which the face of said write head is covered with silicon 

1. A display panel including in combination, a plurality of display modules each of which is capable of forming and visually displaying a character, a plurality of lines of display modules provided by the arrangement of groups of said display modules in side by side relationship within each line, a plurality of rows of display modules provided by the modules in said lines disposed one above the other as an endless blanket, a module write position in which characters are formed in modules of one of said lines disposed therein, a read position in which lines of modules having characters formed therein are displayed to view, indexing means for moving said blanket to sequentially present a different line to said module write position and respectively remove a line from the read position while presenting a new line to the read position, a write head assembly supported within said panel, a write head writing position, write head moving means for shifting said write head assembly in and out of said write head writing position, transducer means of said write head assembly for receiving and converting character forming signals to visual characters in said modules when said modules are in said module write position and said write head assembly is in write head writing position, pawl means, a blanket stop engaging position of said pawl means, pawl moving means for moving said pawl means into and out of said blanket stop engaging position, and control means for synchronizing said indexing means and said pawl moving means and said write head moving means to present one of said lines in said module write position, said pawl means in said blanket stop engaging position and said write head assembly in said write head writing position such that the write head has moved into position after the pawl means has stopped the blanket.
 2. A display panel in accordance with claim 1 in which each module contains upper and lower hook members formed thereon and a blanket rod is provided between each of said lines with which said hooks engage to form said endless blanket.
 3. A display panel in accordance with claim 2 in which said pawl means includes a plurality of pawls each of which has a blanket rod engaging surface which engages said blanket rod in said blanket engaging position and which is shaped to encompass a portion of the surface of said blanket rod preventing bowing thereof.
 4. A display panel in accordance with claim 2 in which sensing means are provided to sense the presence of a blanket rod in a predetermined position thereof to affect said indexing means to reduce the speed of movement of said blanket as said module write position is approached by one of said lines.
 5. A display panel in accordance with claim 1 in which said pawl means includes a T shaped pawl with one arm thereof formed to embrace said blanket in said blanket engaging position, a pawl shaft, link means attaching the remaining arm of said pawl to said pawl shaft, a track surface formed on said display panel, wheel means on the body of said pawl riding on said track surface and said pawl moving means rocking said pawl shaft for movement of said pawl in and out of said blanket engaging position.
 6. A display panel in accordance with claim 5 in which said pawl moving means includes first and second link arms, a first pivotal attachment connecting said link arms, a second pivotal attachment of the remaining end of said first arm and said link means, a breaker arm, a third pivotal attachment connecting the remaining end of said second link arm and said breaker arm, said breaker arm being movable by said control means whereby upon alignment of said first, second and third pivotal attachments said pawl is locked in blanket engaging position.
 7. A display panel in accordance with claim 1 in which each module contains a plurality of pivotally mounted, light reflective, character forming flag members and a display magnet mounted on each flag member whereby the influence of a magnetic field determines the position of each of said flag members and pins of each of said modules formed of a square loop magnetizable material projecting rearwardly of said respective module in operative association with respective display magnets and said transducer means includes magnetizing means cooperable with each of said non-display magnets sequentially to determine the position of said respective flag members by affecting the magnetization of said pins, and a non-display magnet supported within said panel with its magnetic field diposed so that lines pass therethrough prior to entering the module write position, with the field direction of the non-display magnet such that each of said pins as it enters its field is saturated and placed on a known position of the hysterisis curve and continued movement through the field brings respective pins into positions where reversal takes place providing a predetermined magnetization condition of each pin prior to its entry into the module write position.
 8. A display panel in accordance with claim 1 in which said write head assembly includes a write head carrier supporting said transducer means and said transducer means consists of a printed circuit board, posts supporting said printed circuit board on said write head carrier in spaced relation thereto and a write head mounted on said printed circuit board, and in which holes are provided in said printed circuit board through which enlarged head pins project for engagement in said posts, said holes being slightly larger than said pins, friction washers disposed upon said circuit board on either side of said hole, and spring means are provided yieldingly urging said printed circuit board away from said posts and in contact with the heads of said pins providing a friction memory mount.
 9. A display panel in accordance with claim 8 in which said posts are flex rods.
 10. A display panel in accordance with claim 1 in which said write head assembly includes a write head carrier supporting said transducer means and said transducer means consists of a printed circuit board, posts supporting said printed circuit board on said write head carrier in spaced relation thereto and a write head mounted on said printed circuit board, and in which each of said modules includes a plurality of rearwardly projecting pins and each of said write heads includes a plurality of solenoids each of which is received to receive a respective pin as the core thereof with the entrance to said solenoid being in the form of a bell mouth.
 11. A display panel in accordance with claim 10 in which the face of said write head is covered with silicon rubber. 